1. Field of the Invention
The present invention relates to an improvement in a carburetor having a main fuel passage communicating with a main nozzle and a slow fuel passage leading to slow fuel ports such as idle port.
2. Description of the Prior Art
Due to the shortage of crude oil, there have been made various approaches to alcoholic fuel which is comparatively easy to produce, as a fuel substituting for the gasoline. The alcohol, however, has a calorific power which is about a half of that of the gasoline. Therefore, for obtaining the engine output equivalent to that produced by gasoline, it is necessary to use the alcoholic fuel at a rate which is about twice as large as that of the gasoline. Therefore, if the engine is required to operate with a carburetor of the type mentioned above, the carburetor has to have a main fuel flow rate characteristic and a slow-fuel flow rate characteristic optimized for the use of the alcoholic fuel.
At the present stage, however, the alcoholic fuel is not spread commercially so widely, and only gasoline is available in most of the gas stations. From this point of view, it is highly desirable that the aforementioned characteristics of the carburetor can be switched as desired between the mode for operation with gasoline and the mode for operation with alcoholic fuel. The switching of the characteristics of the carburetor is required also when the condition of engine operation is changed due to change of atmospheric pressure and so forth, even when the same fuel is used continuously.